Conventionally, a known valve timing control apparatus includes a housing, which is rotatable with rotation of a crankshaft and a vane rotor, which is rotatable with rotation of a camshaft and having a vane to partition an operation chamber in the housing in a rotative direction. Such a valve timing control apparatus is configured to change a rotation phase of the vane rotor relative to the housing by supplying a hydraulic fluid into the operation chamber. According to US Patent 2002/0139332 A1 (JP-A-2002-357105), a valve timing control apparatus includes a control valve for controlling a flow of a hydraulic fluid supplied into an operation chamber. The control valve is further configured to control a flow of a hydraulic fluid for locking or releasing a housing relative to a vane rotor.
The valve timing control apparatus of US PATENT 2002/0139332 A1 includes a lock pin for locking the housing relative to the vane rotor by discharging a hydraulic fluid from an inner chamber (lock chamber) of a recess. In addition, the lock pin is configured to release the lock by supplying a hydraulic fluid into the lock chamber. The valve timing control apparatus of US PATENT 2002/0139332 A1 further includes an electromagnetic control valve for controlling a flow direction of a hydraulic fluid relative to an advance chamber and a retard chamber (operation chambers). The electromagnetic control valve is further configured to control an amount of a hydraulic fluid supplied to one of the advance chamber and the retard chamber and discharged from the other of the advance chamber and the retard chamber. The valve timing control apparatus of US PATENT 2002/0139332 A1 further includes another electromagnetic control valve configured to selectively switch a port, which is communicated with a lock chamber, to an outlet port of a supply source or a port communicated with an oil sump. That is, the valve timing control apparatus of US PATENT 2002/0139332 A1 includes two control valves, one being for a phase control and the other one being for a lock pin control.
In such a valve timing control apparatus, when the control valve for a phase control is in a specific region, a communication port of the operation chamber and a communication port of the lock chamber is communicated respectively with a communication port of the supply source and a discharge port. In such a region, a hydraulic fluid is supplied from the supply source into the operation chamber according to a position of the spool valve controlled by the control valve for a phase control. In addition, a hydraulic fluid is discharged from the lock chamber into a lock passage according to a switching operation of the control valve for a lock pin control. Thus, the lock pin biased from a spring locks the rotation phase. Alternatively, the control valve for a phase control may be in a region to communicate the communication port of the operation chamber and the communication port of the lock chamber with the communication port of the supply source. In such a region, a hydraulic fluid is supplied from the supply source into both the operation chamber and the lock chamber by controlling the two control valves. Thus, the rotation phase can be changed while the lock is released.
However, the valve timing control apparatus of US PATENT 2002/0139332 A1 includes the two control valves for performing a phase control and a lock pin control separately. Accordingly, a large space is needed for accommodating the two control valves. In addition, a large amount of electricity may be consumed to drive the two control valves. Accordingly, it is preferable to perform a phase control and a lock pin control by using a single element of a control valve. However, when the lock pin is operated to lock the rotation phase in such a valve timing control apparatus, the lock pin needs to be locked in an intermediate phase between a maximum advanced phase and a maximum retard phase, while the phase is changed to an advance side or a retard side. In such a condition, when the rotation speed is changed at a high advance speed or a high retard speed, the lock pin cannot be fitted into a lock hole steadily. In such a case, the lock pin may pass the lock hole. Consequently, the phase lock may not be properly performed.